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Tip of the Day
Language: Java
Expertise: Advanced
Jun 15, 2004

Execute a .jar File Without All the Usual Debugging

In order to execute a .jar file using Java's -jar jarfile command, the manifest file needs to have the classpath defined. This would look something like:

Manifest-Version: 1.0
Sealed: true
Main-Class: com.Calculator
Class-Path: "C:\Java\ant\lib\ant.jar"
So the execution command would be:

java jar calculator.jar 
If this is not defined, you will get an error. Rather than regenerate the .jar file with a new manifest, you can instead execute the .jar file with the following command:

java -cp "C:\Java\ant\lib\ant.jar";.\calculator.jar com.Calculator
Note that you are using the java command here instead of the jar command. You need to specify the classpath as well and the java command's limitation is such that you cannot specify both jar and cp option at the same time, the above command has to be used. Another alternative is to specify the classpath in a separate manifest file itself and then execute the .jar file using the jar command using this external manifest file.

Puneet M. Sangal
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